everyday driving (choke/accel pump) skews readings. For main metering I would go out on the highway till it's warm then pull over & replace one plug (on the hottest cyl) with a new plug & unhook the accel pump rod then ease back on the highway & drive for 10 miles or so staying out of the power system then shut the ign off/put it in neutral/foot off of the gas & coast to the side of the road & pull that plug (take a pic) & see what you see